1. FIELD OF THE INVENTION
The present invention relates to an oil supply device for a valve operating system having a hydraulic tappet in an internal engine.
2. DESCRIPTION OF THE PRIOR ART
A valve operating mechanism is known in the prior art, which has hydraulic tappets provided therein so that the clearances between valve operating cams and intake and exhaust valves need not be adjusted (see Japanese Utility Model Application Laid-open No. 12607/83).
A valve operating mechanism is also known in the prior art, in which an oil supply line for supplying an oil into a hydraulic tappet and a lubricating oil line for supplying an oil to the portions to be lubricated such as bearings or the like of a valve operating cam shaft are provided in a cylinder head of an engine body (see Japanese Patent Application Laid-open No. 226217/84).
In such valve operating systems having hydraulic tappets, there are commonly provided an oil supply line for supplying an oil into a hydraulic tappet and a lubricating oil line for lubricating the portions to be lubricated such as bearings or the like of a valve operating cam shaft. With the conventional such systems, however, various problems are encountered. For example, if the hydraulic pressure within the oil supply line into the hydraulic tappets is excessively increased, a relief valve in such line is opened, resulting in a difficulty of supplying the oil to the bearings of the valve operating cam shaft and further in an inappropriate control in flow rate in the oil supply line into the hydraulic tappets and the lubricating oil line to the bearings of the valve operating cam shaft.
In addition, the incorporation of air in the hydraulic oil supplied into the hydraulic tappets causes the interference with the operation of the hydraulic tappets and hence, it is requisite to provide an air bleed mechanism in the oil supply line into the tappets. On the contrary, even if a little air is incorporated in the lubricating oil being supplied to the portions to be lubricated such as bearings or the like of the valve operating cam shaft in the valve operating system, any interference cannot be made with the lubrication of such portions to be lubricated, but still, for the purpose of providing a more effective lubrication, it is desirable to prevent air from being incorporated into the lubricating oil as well. Further, it is desirable to restrain an increase in weight and size of and a reduction in strength of the cylinder head even if the oil supply line into the hydraulic tappets and the lubricating oil line to the portions to be lubricated are provided in the cylinder head.
Moreover, it is desirable to be able to easily achieve the maintenance when clogging occurs in the oil supply line, the lubricating oil line and the like.